KR100295293B1 - Noise reduction type input device - Google Patents

Abstract

PURPOSE: A noise reduction type input device is provided to previously sense the potential level of an outer input signal to vary the resultant switching potential so as to assure the fair and stable noise margin to the variance of potential level used in the input signal. CONSTITUTION: A input potential level sensing unit(10) senses the potential level of an outer input signal to output a first level control signal or a second level control signal in accordance with the sensed potential level. A switching potential variable unit(20) is switched in a first voltage corresponding to half of the first level when the first level control signal was input from the input potential level sensing unit(10), and is switched in a second voltage corresponding to half of the second level when the second level control signal was input from the potential level sensing unit(10).

Description

Noise Reduction Input Device

The present invention relates to a noise reduction input device. More particularly, the present invention relates to a potential level of an external input signal by detecting a potential level (TTL / CMOS level) of an external input signal and changing a switching potential according to the potential level. The present invention relates to a noise reduction input device capable of ensuring a stable noise margin, respectively.

In general, an input buffer as an input device used in a semiconductor memory device is a device that buffers external input data to produce an internal signal having a potential level sufficient to drive an external peripheral circuit. Inverters are mainly used.

In general, a semiconductor memory device is divided into a case where an external input signal is a CMOS level and a case where a transistor-transistor logic (TTL) level is used.

1 is a circuit diagram showing an example of a conventional input device using a CMOS circuit.

First, when the external input signal Vin is at the CMOS level, the high potential level signal is the power supply potential Vcc level, and the low potential level signal is the ground potential Vss. For example, when operating at 5V, 5V is sent as a high potential level signal and 0V is sent as a low potential level signal.

On the other hand, when the external input signal is used as the TTL level, a signal of 2.4V or more is input as the high potential level signal, and a signal of 0.8V or less is input as the low potential level signal. However, in this case, in order to perform a compatible operation with respect to the input signal of the TTL level, an input device having a voltage of about 1.6 V corresponding to the middle value of the high potential and low potential signals is configured as a switching point.

Therefore, in the case of an input device compatible with the TTL level signal, when the externally input signal is the TTL level, the switching potential corresponds to the intermediate value of the input signal. Therefore, the noise is equally applied to the high potential level signal or the low potential level signal. When the external input signal is at the CMOS level, a large noise margin (see also the second (a)) is secured for the high potential level signal, while a noise margin is obtained for the low potential level signal. There is a problem to be reduced (see also second (b)).

Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to ensure a stable and stable noise margin for each change when the level of the potential used as the high potential level and the low potential level of the input signal changes. In order to provide a noise reduction input device capable of detecting a potential level of an external input signal in advance and thus changing the switching potential.

1 is a circuit diagram showing an example of a conventional input device.

2 is a diagram showing a difference in securing noise margins according to the potential level (TTL / CMOS level) of an input signal in a conventionally used input device.

3 is a block diagram showing a noise reduction input device according to a first embodiment of the present invention.

4 is a block diagram showing a noise reduction input device according to a second embodiment of the present invention.

5 is a block diagram showing a noise reduction input device according to a third embodiment of the present invention.

6 is a block diagram showing a noise reduction input device according to a fourth embodiment of the present invention.

FIG. 7 is a detailed circuit diagram showing an example of the input potential level detecting means shown in FIGS.

* Explanation of symbols for main parts of the drawings

10: input potential level detection means 20, 30, 40: switching potential variable means

50: comparison unit 60: reference potential generating unit

In order to achieve the above object, the noise reduction type input device according to the present invention is an input device that receives an external input signal input from the outside to make an internal signal, and detects the potential level of the external input signal, thereby detecting the potential level level. An input potential level sensing means for outputting a first level control signal at the first level and a second level control signal if the detected potential level is a second level, and a first level control signal from the potential level sensing means; Switching operation is performed at a first voltage corresponding to 1/2 of the first level when inputting the input signal, and corresponding to 1/2 of the second level relative to the first level when inputting the second level control signal from the potential level sensing means. And a switching potential varying means at a second voltage.

The above and other objects and features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram illustrating a noise reduction input device according to a first exemplary embodiment of the present invention, and detecting whether a potential level of an input signal (in) input from the outside is a transistor-transistor logic (TTL) level or a CMOS level Input potential level detecting means (10) for outputting a control signal (ctrl); A pull-up unit MP1 connected between a power supply potential Vcc and an output terminal and controlled by the input signal in, and connected between the output terminal and a ground potential Vss. The first pull-down unit MN1 whose operation is controlled by an input signal in, and a control signal connected between the output terminal out and the ground potential, which is an output signal of the input potential level sensing means 10 and switching potential varying means (20) consisting of second pull-down sections (MN2, MN3), which are selectively operated by ctrl and controlled by the input signal.

The noise reduction input device having the above configuration detects whether the potential level of the input signal to be applied is TTL level or CMOS level by the input potential level sensing means 10 and outputs control signals ctrl of different potential levels. In this case, when an input signal is input at the CMOS level, a control signal having a 'low' level is output as the output signal ctrl of the input potential level detecting means 10, thereby providing the control signal of the switching potential varying means 20. The second N-channel MOS transistor MN2 constituting the second pull-down part is turned off. Thus, for example, when the 5V power supply potential is used, the switching potential of the output out becomes 2.5V, which is an intermediate value between the ground potential (0V) and the power supply potential (5V).

However, when the input signal is input at the TTL level, the 'high' level control signal ctrl turns on the second N-channel MOS transistor MN2 constituting the second pull-down portion of the switching potential varying means 20. By turning it on, the potential at the output (out) is quickly grounded, allowing switching to take place at 1.6V, which is relatively lower than 2.5V.

By the above operation, the size of the pull-up part and the pull-down part of the input device is changed to have different switching potentials (1.6 / 2.5V) according to the potential level (TTL / CMOS level) of the input signal. Therefore, it is possible to secure a fair and stable noise margin for each of the high potential and low potential signals regardless of the potential level (TTL / CMOS level) of the input signal.

Although not shown in the drawings, the switching potential varying means 20 is connected between the power supply potential and the output terminal, and is configured between the power supply and the output terminal, and a first pull-up part whose operation is controlled by an input signal. A second pull-up part which is selectively operated by a control signal ctrl which is an output signal of the level sensing means 10 and whose operation is controlled by the input signal, and is configured between the output terminal and the ground potential and It can be configured as a pull-down part whose operation is controlled.

In addition, the noise reduction input device having the above-described configuration may also make the switching potential of the output terminal different according to the potential level (TTL / CMOS level) of the input signal by the selective operation of the second pull-up unit.

4 is a block diagram illustrating a noise reduction input device according to a second embodiment of the present invention, and outputs a control signal ctrl by detecting a potential level (TTL / CMOS level) of an input signal in that is input from the outside. Input potential level sensing means (10); A first switching element MP1 connected between the power supply potential Vcc and the first node N1 and controlled in operation by a control signal ctrl, which is an output signal of the input potential level sensing means 10, and A second switching element MP2 connected between the potential potential Vcc_int generated by and the first node N1 and selectively operated by the control signal ctrl, and the first node N1 and the output terminal. connected between the output terminal (out) and the operation controlled by the input signal (in) and the output terminal (out) and the ground potential (Vss) connected by the input signal (in) It consists of a switching potential varying means 30 made up of a pull-down element MN1 whose operation is controlled.

The noise reduction input device by the above configuration changes the switching potential by detecting the potential level of the input signal by changing the level of the power supply potential (Vcc) used, and outputs the input potential level detection means (10). The first and second switching elements MP1 and MP2 are selectively turned on according to the signal ctrl to apply the level Vcc and Vcc_int of the power potential to the first node N1 differently. The power supply potential is transferred to the output terminal according to the pull-up device MP3 and the pull-down device MN1 which operate differently according to the potential level of the input signal.

That is, when a CMOS level signal is input, the output signal ctrl of the input potential level detecting means 10 turns on the first switching element MP1 to generate a relatively high power supply potential Vcc. When the control signal ctrl turns on the second switching element MP2 when the signal is input to the node N1 and the signal is input at the TTL level, the internal power potential Vcc_int is relatively low. To node N1. As a result, the switching potential of the output (out) is lower in the case of the TTL level than the CMOS level, and ensures a fair and stable noise margin for the high potential and low potential signals of each potential level. It becomes possible.

5 is a block diagram illustrating a noise reduction input device according to a third embodiment of the present invention. The control signal ctrl is detected by detecting whether a potential level of an input signal in, which is input from the outside, is a TTL level or a CMOS level. An input potential level sensing means for outputting; A comparator 50 for comparing the potential of the external input signal in with the first node N1 and outputting the comparison signal, and a first reference potential generated inside the first node N1 and the device; a first switching element MN1 connected between vref1 and selectively operated by a control signal ctrl, which is an output signal of the input potential level sensing means 10, and the first node N1 and an interior of the element. A switching potential variable consisting of a second switching element MN2 connected between the second reference potentials vref2 generated at and selectively operated by a control signal ctrl which is an output signal of the input potential level sensing means 10. Means 40.

The noise reduction type input device having the above configuration selectively turns the first and second switching elements MN1 and MN2 according to the output signal ctrl of the input potential level detecting means 10 when the noise reduction type input device is configured as a comparison device. By turning on, the reference voltages Vref1 and Vref2 serving as inputs of the comparator 50 are differently applied to the first node N1. As a result, since the reference potentials Vref1 and Vref2 vary according to the potential level of the input signal, the switching potential of the output out is also changed according to the potential level of the input signal, so that it is fair and stable according to the potential level of each input signal. It is possible to secure a noise margin.

FIG. 6 is a block diagram showing a noise reduction input device according to a fourth embodiment of the present invention. A group consisting of the input potential level detecting means 10 and the switching potential varying means 20 shown in FIG. The case where it has 2 or more of B) is shown. In this case, it is possible to divide the input signal into two or more groups A and B so as to have different switching potentials, and the data signal data and the address signal add to the input terminals of the groups A and B. ) May be input respectively.

FIG. 7 is a detailed circuit diagram showing an embodiment of the input potential level detecting unit 10 shown in FIGS. 3 to 6, and the reference potential generator 60 generates a reference voltage Vref. And, during a specific operation (here, 'mode set' operation; setting in CMOS mode or setting in TTL mode) the external input signal in and the reference potential Vref generated by the reference potential generating unit 60. Comparing unit 50 of the current mirror structure to be compared and the output unit 70 for outputting a control signal (ctrl) for detecting the potential level of the external input signal as a comparison result of the comparison unit 50 .

The reference potential generator 60 is formed in the form of a voltage divider consisting of two resistors R1 and R2 connected in series between a power supply potential and a ground potential.

Thus, the input potential level detecting means 10 determines whether the input signal is high or low regardless of the change in the power supply potential, and accurately outputs the output signal ctrl of the comparison unit 50 to the transmission gate MT1,. After transfer by the selective operation of MT2, the control signal ctrl is constantly maintained at the output terminal by latching it by two inverters I1 and I2 connected to the input / output terminals.

In the case of using the 5V power potential, the present invention will be explained by changing the size of the pull-up and pull-down parts of the input device, changing the level of the power potential used in the input device, or comparing the input devices. In the case of a device, when the externally input signal is input as a TTL (transistor-transistor logic) level signal by changing the potential of the comparison voltage used as the reference potential (high potential signal is 2.4V or more, low potential When the signal is input below 0.8V, the high potential and low potential level of the external input signal is sensed so that the input device switches at 1.6V, and when the external input signal is input at the CMOS level (high potential). When the signal is input at 5V and the low potential signal is input at 0V), the switching operation occurs at 2.5V. Due to the generation of the selective switching potential, it is possible to ensure a noise margin equal to the potential level (TTL / CMOS level) of each input signal.

As described above, according to the noise reduction type input device according to the present invention, the potential level of the voltage used as the high potential and the low potential of the external input signal is first detected whether the TTL level or the CMOS level is switched to different levels according to the level. By changing the switching potential to have a potential, a more stable noise margin is ensured for each potential level, and thus there is a very excellent effect of significantly reducing noise over the entire operation.

In addition, preferred embodiments of the present invention are disclosed for the purpose of illustration, those skilled in the art will be able to make various modifications, changes, additions, etc. within the spirit and scope of the present invention, such modifications and modifications belong to the scope of the claims You will have to look.

Claims (15)

An input device that receives an external input signal input from an external source and generates an internal signal, wherein the potential level of the external input signal is sensed, and when the detected potential level is a first level, a first level control signal is output and detected. An input potential level sensing means for outputting a second level control signal when the potential level is a second level, and a second equivalent of 1/2 of the first level when the first level control signal is input from the potential level sensing means; A switching potential varying means for switching at one voltage and switching at a second voltage corresponding to one half of a second level which is relatively lower than the first level upon input of a second level control signal from the potential level sensing means; Noise reduction input device characterized in that it comprises a. The apparatus of claim 1, wherein the input potential level detecting unit comprises: a reference potential generating unit for generating a reference potential, a comparison unit for comparing an external input signal with the reference potential during a mode setting operation, and switching the comparison result of the comparison unit; Noise reduction type input device characterized in that the output section for outputting to the potential variable means. The noise reducing input device of claim 2, wherein the comparator comprises a current mirror structure. The noise reduction input device of claim 2, wherein the reference potential generator comprises a voltage divider. The noise reduction input device of claim 4, wherein the voltage divider comprises two resistors connected in series between a power potential and a ground potential. The noise reduction type input device of claim 2, wherein the output unit comprises a transmission gate for transmitting the output signal of the comparator, and a latch stage for latching the signal transmitted to the transmission gate and maintaining the same at the output terminal. . The noise reduction input device of claim 6, wherein the latch stage comprises two inverters having common input / output terminals connected to each other. The switching potential varying means of claim 1, wherein the switching potential varying means is connected between a power supply potential and an output terminal and controlled by an external input signal, and is connected between the output terminal and a ground potential and operated by the external input signal. A second pull connected to the controlled first pull-down part, the output terminal and the ground potential, selectively operated by a control signal which is an output signal of the input potential level sensing means, and controlled by the input signal; Noise reduction type input device characterized in that consisting of a down. 2. The apparatus of claim 1, wherein the switching potential varying means is connected between a power supply potential and an output terminal, the first pull-up unit being controlled by an input signal, and configured between the power supply potential and an output terminal and outputting the input potential level sensing means. And a second pull-up part which is selectively operated by a control signal which is a signal and whose operation is controlled by the input signal, and a pull-down part which is configured between the output terminal and the ground potential and whose operation is controlled by an input signal. Noise reduction input device. 2. The apparatus of claim 1, wherein the switching potential varying means is connected between a power supply potential and a first node and controlled by an control signal which is an output signal of the input potential level sensing means. A second switching unit connected between an internal power supply potential and the first node and selectively operated by the control signal, a pull-up unit connected between the first node and an output terminal and controlled by an input signal; And a pull-down part connected between the output terminal and the ground potential and controlled by the input signal. 2. The apparatus of claim 1, wherein the switching potential varying means comprises: a comparator for comparing an external input signal with a potential of the first node and outputting the comparison signal, and a first reference potential generated inside the device and the first node. An input potential level connected between the first switching unit and a second reference potential generated inside the device, the first switching unit being selectively connected by a control signal which is an output signal of the input potential level sensing means. A noise reduction input device comprising a second switching unit for selectively operating by a control signal which is an output signal of the sensing means. 12. The noise reduction type input device according to any one of claims 8 to 11, wherein the pull-up part comprises a P-channel MOS transistor. 12. The noise reduction type input device according to any one of claims 8 to 11, wherein the pull-down part is formed of an N-channel MOS transistor. The noise reduction input buffer of claim 10, wherein the first and second switching units comprise a P-channel MOS transistor. 12. The noise reduction input buffer of claim 11, wherein the first and second switching units comprise N-channel MOS transistors.